摘要
維修保固是近年來逐漸受到買賣雙方重視的課題，同時也是廠商有效的行銷方法，藉由提供產品的售後保固與維修服務，一方面可以使消費者對於產品品質產生認同感，另一方面可以使廠商在生產過程中更注重產品品質，以降低售後保固維修成本。許多商品的失效與衰退同時受到兩種因素，分別為時間以及使用程度所影響，因此制定此類型商品之保固政策時，須用兩項因素所構成之二維保固模式來分析，此外，由於商品不斷推陳出新，消費者意識也逐漸抬頭，為了維持商品的品質以及可靠度，預防性保養的觀念便逐漸受到重視，將預防保養納入保固政策之中是近年來售後服務的市場趨勢，許多廠商都提供了附帶預防性保養的保固條款，以供消費者做選擇。
過去針對二維保固模式的研究，多以矩形來訂定修復─置換策略的判定區間，且多以單變量方法來分析，因此本研究以雙變量的方式，分析以時間及使用程度兩因素所構成之函數，並加入預防性保養的概念，期望幫助廠商建立一個使買賣雙方皆能滿意的保固政策，做為與消費者制定產品保固契約的依據。本研究提出之模式，是以雙變量韋伯分配為基礎，分析時間以及使用程度所構成之失效函數，由於不同的消費族群對商品的使用方式以及使用程度有所差異，本研究將其分為兩類：低使用率以及高使用率族群，針對不同族群提出兩種策略來做分析：第一種為先到達保固時間，即低使用率族群；第二種為先到達保固使用程度，即高使用率族群，由於無法得知市場上哪一類消費者較多，但廠商對兩種類型顧客同樣重視，因此此兩策略重要性相當，藉由個別策略可以求得在特定情況下的最佳保固政策，再由兩策略之間尋求均衡解使廠商總利潤最大化，最後透過預防性保養的實施，可以使商品的失效降低、增加設備壽命並給予消費者更好的保障。

Abstract
In recent years, warranty has become important with the form of after-sale service. Which enables manufacturers to put more efforts on products’ quality, and as a result, consumers are attracted by the image of better products. In dealing with product deterioration, it may not be satisfactory to consider only the effects of time or age because usage is often another essential factor that accounts for deterioration. Moreover, as new products continuously emerge and consumer’s awareness gradually rises, preventive maintenance has become an important concern in maintaining products’ quality and reliability. In this study, a two-dimensional warranty model is proposed in which customers are expected to perform appropriate preventive maintenance to determine the warranty policy that maximizes the manufacturers’ profit.
Most of the past research about two-dimensional warranty uses univariate methods to analyze the failure model of repairable systems. However, in this study, a bivariate Weibull failure model with preventive maintenance is proposed. Because of the different conditions of usage among customers, this study considers two strategies to determine the warranty policy. One considers that the warranty time may met first, and the other considers that the warranty usage may met first. For equilibrium, such the two types of customers may have about the same size, and their importance are also the same. Accordingly, we can obtain an equilibrium solution that maximize the manufacturers’ profit.

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